1. Field of the Invention
The present invention relates to hinge assemblies and, particularly, to an automatic opening hinge assembly for foldable devices such as portable telephones, portable computers, and so on.
2. Discussion of the Related Art
With the development of wireless communication and information processing technologies, foldable electronic devices such as mobile phones and PDAs (Personal Digital Assistants) are now in widespread use, and consumers may now enjoy the full convenience of high technology products anytime and anywhere. Foldable electronic devices are particularly favoured by a wide range of consumers because of their small size, novel design and ease of use. Use of a foldable design can also avoid accidental activation of keys/buttons of the electronic device during transportation/storage.
The foldable mobile telephone generally includes a cover section and a body section. The cover section and the body section are rotatably interconnected through a hinge assembly, thus allowing the telephone to be switched between an in-use position and a closed position. One kind of hinge assembly employs a cam and a follower, which makes the cover section fold outward from the body section and then hold in an open position. The hinge assembly typically includes a cam having a concave portion, a follower having a convex portion, a shaft having a fixing end, and a spring. The cam and the follower are placed around the shaft. The spring resists the follower to make the concave portion tightly contact the convex portion. The cam, the follower, the shaft and the spring are received in a housing. A flip cover rotates about a main body of the mobile phone by overcoming the force of the spring, thus making the concave portion rotate about the convex portion.
However, a user must open the mobile phone using both hands. This makes the mobile phone awkward to utilize in situations when the user has only one hand free. In addition, the foldable electronic device can only be opened to preset angles, because the cam only stably engages with the coplanar end faces of follower in a few preset positions. In addition, the concave portion of the cam is designed with relatively sharp edges and corners, which are prone to being worn smooth by repeated use. When this happens, the connection between the body and the cover is liable to become loose.
Therefore, a new hinge mechanism is desired in order to overcome the above-described shortcoming.